ASME International

IMPROVEMENT OF  NH FOR GRADE 91 NEGLIGIBLE CREEP AND CREEP FATIGUE
 N STP-PT-014

Annotation

Composite cylinders have been used for over 50 years in commercial, vehicle, defense and aerospace applications. New materials, processes, design approaches and applications have been incorporated during that time. The industry has maintained a high level of safety. The industry has adapted to these changes and has developed new and revised standards to address these changes and to reflect a better understanding of service conditions.

Recommendations are made that the industry:

• Continue to monitor field use and incorporate changes to requirements, standards and codes that reflect knowledge gained for composite pressure vessels,

• Use a failure modes and effects analysis (FMEA) approach to standards, using the knowledge gained from field experience,

• Develop standards for composite pressure vessels that are more performance based to improve both safety and performance,

• Address requirements using performance testing, not by using excessive safety factors,

• Use stress ratios for the various reinforcing fibers that accurately reflect their stress rupture and fatigue characteristics to achieve high reliability, Harmonize testing requirements where practical, Use qualification tests that are appropriate for the application and for the materials and design features of the pressure vessels being used, and

• Consider using fleet leader programs for new materials, designs or applications if there is likely to be a significant safety issue

To support these recommendations, history of use of composite cylinder in aerospace/defense, commercial and vehicle applications is reviewed. This includes review of applications, materials of construction; standards used and field service issues.